How to place ID, PW, etc in my iPhone

I am old on computers and age, but new on iphones, The first function I tried (other than making phone calls) was to download google. The iphone wants me to update my PW, Phone Number, and mailing address In Settings. I update them, but they revert to the old data when I leave Settings. My Apple ID,PW, etc. on
my PC are correct and satisfactory. I’d like to know how to make the iphone the same.